import java.util.List;

public class MyLinkedList{
    // 2、无头双向链表实现
     static  class ListNode{
        public int val;
        public ListNode prev;
        public ListNode next;
         public ListNode(int val) {
             this.val = val;
         }
    }
    public ListNode head;
    public ListNode last;
      public void addFirst(int data){
        ListNode node = new ListNode(data);
        if (head == null) {
            head =  node;
            last = node;
        }else {
            node.next = head;
            head.prev = node;
            head = node;
        }
      }
        //尾插法
        public void addLast(int data){
          ListNode node = new ListNode(data);
          if (head == null) {
              head =  node;
              last = node;
          }else {
              last.next = node;
              node.prev = last;
              last = node;
          }
        }
//任意位置插入,第一个数据节点为0号下标
        public void addIndex(int index,int data){
          if (index < 0 || index > size()) {
              throw new ListIndexOutofException("插入下标不合法");
          }
          ListNode node = new ListNode(data);
          ListNode cur = head;
          if (index == 0) {
              addFirst(data);
              return ;
          }
          if (index == size()) {
              addLast(data);
              return ;
          }
            for (int i = 0; i < index; i++) {
                cur = cur.next;
            }
            node.next = cur;
            node.prev = cur.prev;
            cur.prev.next = node;
            cur.prev = node;
        }
//查找是否包含关键字key是否在单链表当中
      public boolean contains(int key){
          ListNode cur = head;
          while(cur != null) {
              if (cur.val == key) {
                  return true;
              }
              cur = cur.next;
          }
          return false;
      }
        //删除第一次出现关键字为key的节点
        public void remove(int key){
          ListNode cur = head;
          while(cur != null) {
              if (cur.val == key) {
                  if (cur == head) { //1. 为第一个节点的情况
                      head = head.next;
                      if (head != null) { //因为当只有一个节点时head=head.next会空指针异常，所以此处要判断
                          head = head.next;
                      }
                  } else {
                      cur.prev.next = cur.next;
                      if (cur.next != null) {//2. 为中间节点的情况
                          cur.next.prev = cur.prev;
                      } else { //3. 为最后一个节点的情况
                          last = last.prev;
                      }
                  }
                  return;
              }
              cur = cur.next;
          }
      }
          //删除所有值为key的节点
        public void removeAllKey(int key){
            ListNode cur = head;
            while(cur != null) {
                if (cur.val == key) {
                    if (cur == head) { //1. 为第一个节点的情况
                        head = head.next;
                        if (head != null) { //因为当只有一个节点时head=head.next会空指针异常，所以此处要判断
                            head = head.next;
                        }
                    } else {
                        cur.prev.next = cur.next;
                        if (cur.next != null) {//2. 为中间节点的情况
                            cur.next.prev = cur.prev;
                        } else { //3. 为最后一个节点的情况
                            last = last.prev;
                        }
                    }

                }
                cur = cur.next;
            }
        }
      //得到单链表的长度
    public int size(){
          int len = 0;
       ListNode cur = head;
       while (cur != null) {
           len++;
           cur = cur.next;
       }
       return len;
      }
      public void display(){
       ListNode cur = head;
       while (cur != null) {
           System.out.print(cur.val + " ");
           cur = cur.next;
       }
          System.out.println();
    }
         public void clear(){
          head = null;
          last = null;
       }
}

